Clamping sleeves for TIG burners generally are provided with slits at the clamping end adjacent the compression surfaces which may be cup-shaped or tapered, e.g. frustoconical, so that the axial slits define tongues which can be pressed against the electrode, usually a tungsten electrode.
Upon threading of the compression cap onto the clamping sleeve housing, the clamping end of the clamping sleeve is pressed by the conical or cup-shaped seat of the clamping sleeve housing inwardly against the electrode.
The electrode is thus held between the tongues. Upon loosening of the compression cap, the clamping force upon the electrode can be relieved and the electrode can be axially shifted to accommodate a variety of working conditions or can be replaced by another electrode.
The welding current is transferred from the clamping sleeve housing and the clamping sleeve, both of which are formed from highly conductive metals, to the electrode. Usually the welding current is applied to the electrode at a location close to the welding site and for this purpose, the throughgoing bore of the clamping sleeve may be stepped so that the electrode will come in contact with the tongues only over a limited portion of the length of the sleeve, i.e. the metallic contact is established substantially only at the ends of the tongues adjacent the compression surface and the seat.
As a consequence, the current density in the region of the seat of the sleeve housing and the ends of the tongues of the sleeve is especially high.
In addition, the thermal loading in this region is especially high even though tungsten, the electrode material, and copper or copper-tellurium alloys, the material from which the clamping sleeve and the sleeve housing are fabricated are good thermal conductors.
In spite of the good thermal conductivity of these materials, it is uncommon for the temperature at the clamping ends of the tongues to exceed allowable limits. As a consequence, undesirable deformations, twisting and distortions and even burn-off of the tongue ends can occur so that the clamping sleeve becomes unusable.
An improvement in the conduction of heat away from the limited contact zones is scarcely possible because of the small dimensions of the contact zones.
For similar reasons, cooling systems which are customarily used in the burner head in which the housing is received are generally not maximally effective at the end of the housing and sleeve at which maximum current transfer and maximum heat generation occur.